Impact of Urban Expansion and Thermally-Driven Flows on Madrid's Local Meteorology.

Over the past five decades (1970–2020), Madrid's population has doubled, while its urban area has expanded fivefold. By 2037, projections estimate further urban growth of 1.15 to 2.14 times compared to 2010, alongside a 15% population increase (INE, 2022). This rapid urbanization drives to poorer city air quality and an energy consumption increase, and can alter the mesoscale and local atmospheric circulations, affecting the Urban Heat Island (UHI) effect.

This study evaluates the impact of Madrid’s urban expansion on local meteorology using the mesoscale WRF model configured with the BEP-BEM urban parameterization (Martilli et al., 2002; Salamanca et al., 2010, Carbone et al., 2024). Urban parameters are integrated based on the city’s growth from 1970 to 2020. Results show that areas with increased urban fraction experience higher near-surface air temperatures, especially at night. Urbanization also modifies the Surface Energy Balance (SEB) and turbulent transport. These findings underscore the role of urban-induced changes in local meteorology and highlight the need for climate adaptation strategies to mitigate the effects of urban expansion on air quality and thermal comfort in Madrid.

This work is being developed in the framework of the MULTIURBAN-II ("Impacts of mesoscale thermally-driven flows on the urban heat island, local meteorology, and air quality in complex environments in the city”) research project, which will be also presented. This project analyses the dynamic and thermal impacts of these flows in different city zones, the role of turbulent mixing, their effects on UHI, and broader implications. To achieve these objectives, both field campaign data from meteorological stations (including radiative and turbulent fluxes in urban and rural environments) will be combined with simulations from the WRF model, enhanced with the WRF-Comfort urban canopy model (Martilli et al., 2024). This integrated approach allows us to assess the spatial and temporal dynamics of thermal comfort under the influence of breezes and validate the model's performance.